staging:iio:ad7476: Do not return error code in interrupt handler

The interrupt handler should only ever return one of the three irqreturn_t
constants and not an error code. Also make sure to always call
iio_trigger_notify_done before leaving the trigger handler.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/ad7476_ring.c

@@ -31,7 +31,7 @@ static irqreturn_t ad7476_trigger_handler(int irq, void  *p)
 
 	rxbuf = kzalloc(indio_dev->scan_bytes, GFP_KERNEL);
 	if (rxbuf == NULL)
-		return -ENOMEM;
+		goto done;
 
 	b_sent = spi_read(st->spi, rxbuf,
 			  st->chip_info->channel[0].scan_type.storagebits / 8);